Generating sequence diagrams using call trees

ABSTRACT

A software tool is provided to analyze static source code. Source Code files are selected to define the project work space. A class and a method in the class are selected from said selected source code files. The tool generates a Call Tree as an ordered recursive sequence of all method calls in different classes or their instances that are invoked by said selected method in said selected class. A Sequence Diagram is generated from said Call Tree. The tool remembers all updates to the Call Tree used to generate the Sequence Diagram. This information is used when a generated Sequence Diagram is impacted due to changes made to any source code file included in the project.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a software analysis tool and, moreparticularly, to an integrated reverse engineering and designworkproducts maintenance tool for object-oriented type programminglanguages, such as, Java, and the like.

2. Background and Related Art

A great variety of tools are available in the software industry to aidin developing, maintaining and updating software programs. One of thedifficulties with maintaining and updating software is the ability tokeep track of work products generated and determining the affected workproducts when a source code file that was used to generate the workproducts is modified. Various approaches have been used to provide toolsto aid in analyzing and maintaining software and a number of theseapproaches are designed for object-oriented coding using sequencediagrams.

For example, the UML (Unified Modeling Language) uses sequence diagramsto capture interactions between software components, such as, objects,methods, modules, entire software applications, sub-systems, and thelike. Programs, such as AQTime, employ a static profiler that does notrun the application but creates a UML-style diagram that graphicallyrepresents the sequence of routine calls. Classes are shown as entities,and source-code calls between methods of different classes are treatedas messages.

One of the difficulties with the AQTime tool resides in the fact thatthe tool is required to operate on the static executable compiled codewith appropriate debug information. Since the AQTime tool operates onexecutable code, it has to rely entirely on the debug information in theexecutable files which information exists only at the level of classes.

On the other hand, tools, such as DYNO, draw sequence diagrams for a setof classes at runtime. DYNO instruments the classes for which thediagram needs to be drawn, such that, when the classes are run, therelevant data can be collected to draw the diagram. One of thedifficulties with DYNO, then, is that it requires a runtime environmentwhile working with files that need to be deployed on an applicationserver or some such other software to be executed.

Although the use of sequence diagrams is key to work products that areused to capture the sequence of messages passed between differentclasses in typical applications, such use is generally limited to thelow level design phase of the application development project. Thereason for limiting to the low level design phase is that creating thesediagrams for the first time in a project is usually not as difficult andinvolved as maintaining these diagrams in synch with the changes in codethat happen during the later phases of a project.

Accordingly, known software analysis tools fail to provide a simpleapproach such as to operate directly on object oriented source code, ina reverse engineering manner, such as to identify the impacted workproducts when any of the source code files of an application program aremodified. The ability to readily identify work products impacted bychanges in some code files permits easy updating and maintenance of suchproducts.

SUMMARY OF THE PRESENT INVENTION

In accordance with the present invention, a software tool is providedthat allows for the creation of Sequence Diagrams directly fromapplication source code. The Sequence Diagrams are used to analyze theeffect of any updates and changes made to the source code file of theapplication program. The Sequence Diagrams are generated using calltrees derived from the source code using the Code Tree Analyzer tool, inaccordance with the present invention.

The Code Tree Analyzer tool operates within a defined project workspaceof the application program. The project work space contains the completepaths of the source code files, such as Java source code files, that areto be analyzed to produce work products or design artifacts. Classes theuser does want to include in the work products are identified in a list.The tool analyzes the source code and generates UML-compatible modelfiles for the sequence and class diagrams, and text and rtf (rich textformat) files containing the call tree. The tool remembers the workproduct data that have been created. This data is used later todetermine the impacted products when any of the source code files in theapplication program are modified.

To determine impacted work products, the tool maintains a list of sourcecode files. Each time a project is opened, this list is updated with thelatest time stamps of the source code files. The tool maintains a listof work products that were created using the tool and the source codefiles that were used to create each work product. Once a project isopened, the tool compares the time stamps of the source code files thatwas saved in the previous run with the time stamps of the files in thelatest run. A difference in time stamps is taken as an updated sourcecode file. All work products that have used this source code file aremarked as impacted. In addition, the impact to design artifacts thatresult from manual changes made to the source code files can be analyzedand updated using the tool. Thus, the Code Tree Analyzer tool providesan integrated reverse engineering and design work products maintenancearrangement for programming languages, such as, the Java ProgrammingLanguage.

Accordingly, it is, an object of the present invention to provide animproved code analyzer tool.

It is a further object of the present invention to provide a codeanalyzer tool that is simple, fast and easy to operate.

It is yet a further object of the present invention to provide a codeanalyzer tool that effectively operates directly on source code.

It is still a further object of the present invention to provide a codeanalyzer tool that provides a way to simply identify the impact ofchanges in source code files of an application program on the variouswork product elements of the program.

It is yet still a further object of the present invention to provide acode analyzer tool that substantially reduces the effort of determining,keeping track and synchronizing the effect of changes to the source codefiles of an application program.

It is yet another object of the present invention to provide a code treeanalyzer tool that directly analyzes application source code andproduces both sequence diagrams from call trees and class diagrams, eachof which are displayed and which may be modified, updated and varied.

It is still another object of the present invention to provide a codetree analyzer tool that remembers manual updates made by the user to thefiltered call trees so that in later runs of the tool, when a workproduct, impacted by source code changes, is recreated, the tooldisplays these manual updates to the user and allows the user to reapplythese updates to the new call tree.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a block diagram illustrating an exemplary hardwareenvironment which may be used to carry out the preferred embodiment ofthe invention.

FIG. 2 shows a Sequence Diagram derived from a Java code snippet exampleused to show the manner of forming a Call Tree.

FIG. 3 is a flow chart diagram representing the flow process of the basemodel of the Code Tree Analyzer tool, in accordance with the presentinvention.

FIGS. 4A-4E is a flow chart illustrating the main process of the CodeTree Analyzer tool, in accordance with the present invention.

FIG. 5 is a flow chart illustrating a process for creating a newproject, as identified in the main process of FIGS. 4A-4E.

FIG. 6 is a flow chart illustrating a process for creating a new timestamps file, as identified in the main process of FIGS. 4A-4E.

FIG. 7 is a flow chart illustrating a process for creating a new datafile, as identified in FIGS. 4A-4E.

FIG. 8 is a flow chart illustrating a process that acts to resolve thesymbol table, as identified in FIGS. 4A-4E.

FIG. 9 is a flow chart illustrating a process for generating a CallTree, as identified in FIGS. 4A-4E.

FIG. 10 is a flow chart illustrating a process for rendering a SequenceDiagram from the Call Tree, as identified in FIGS. 4A-4E.

FIG. 11 is a flow chart illustrating a process for rendering a ClassDiagram from the Code Tree Analyzer tool.

FIG. 12 is a drawing of a screen shot showing an example of a SequenceDiagram, as rendered by the Code Tree Analyzer tool.

FIG. 13 is a drawing of a screen shot showing an example of a ClassDiagram, as rendered by the Code Tree Analyzer tool.

DETAILED DESCRIPTION

In the following description of the preferred embodiment, reference ismade to the accompanying drawings which form a part hereof, and in whichis shown by way of illustration a specific embodiment in which theapplication may be practiced. It is to be understood that otherembodiments may be utilized and changes may be made without departingfrom the scope of the invention.

FIG. 1 is a block diagram illustrating an exemplary hardware environmentused to implement the preferred embodiment of the invention. In thisexemplary hardware environment, a computer system arrangement 1 mayinclude a central processing unit (CPU) 3, memory 5, data storage device7, data communications device (DCD) 9, input device 10 and displaydevice 29. Other peripheral devices may also be included. The inputdevice and storage device are connected to the system bus 31 throughrespective interface units I/F while the display device is connected tothe system bus through graphics board 35. The computer system 1 may beconnected locally or remotely to fixed and/or removable data storagedevices, such as, storage device 7. The computer system 1 may also beconnected to other computer systems 19 through DCD 9.

The present invention may be implemented using one or more computerprograms that form the Code Tree Analyzer tool, which tool executesunder control of the operating system (OS) 21, such as, Windows, DOS,OS/2, AIX, UNIX, MVS, etc. The stored Code Tree Analyzer tool (CTA), asrepresented by block 23, causes the computer system 1 to operate onstored static application source code files, as represented by block 25.The resulting work products are stored as data, shown by block 27. Thus,in accordance with the present specification, the invention may beimplemented as a machine process or article of manufacture by usingstandard programming and/or engineering techniques to produce software,firmware, hardware or any combination thereof.

The Code Tree Analyzer, as represented by block 23, and operating system21 are tangibly embodied or readable from a computer-readable device ormedia, such as memory 5, data storage device 7 and/or datacommunications device 9, thereby making a computer program product orarticle of manufacture, according to the invention. As such the term“article of manufacture” and “computer program product” as used hereinare intended to encompass a computer program accessible from anycomputer readable device or media.

Code Tree Analyzer 25 and operating system 21 both include instructionswhich, when read and executed by the computer system 1, cause thecomputer system to perform steps to process and analyze applicationsource code 25, in accordance with the invention. Under control of theoperating system, the Code Tree Analyzer code may be loaded from any ofa variety of sources into memory 5. Source code 25 to be analyzed willbe described in terms of the Java programming language although, it isclear that with minor modifications, other object-oriented programminglanguages may also be analyzed.

In accordance with the present invention, the Code Tree Analyzer tool isbuilt around Sequence Diagrams as a visual representation of Call Treedata structures. The Call Tree data structure is a tree structure thatis created by recursively determining method calls on classes or theirinstances starting at a specified method in a class (as input). Thefollowing example demonstrates the process used to generate a Call Treefrom Java source code in the Code Tree Analyzer tool. Although theexample and the discussion is in terms of the Java programming language,it is clear that the process described is not restricted to the Javaprogramming language and could readily be applied to other programminglanguages as well.

The purpose of determining the Call Tree is to form a data structure touse to derive a Sequence Diagram. The Sequence Diagram begins with amethod invocation on a class. In the context of the Code Tree Analyzertool, this has been called the “start point”. A start point is a classname and method name combination from where the tool starts creating theSequence Diagram. This is taken as one of the inputs from the user inthe Code Tree Analyzer tool.

The following three Java code snippets are used as a simple example todemonstrate the process of forming a Call Tree and Sequence Diagram.Each line of the code snippets has been numbered for reference in thedescription.

Code Snippet 1: ClassA 1 public class ClassA { 2 3  /*The constructorfor Class A */ 4  public ClassA ( ) { 5 6  } 7 8  /*A method in class A*/ 9  public void method1A(String arg1) { 10 11    /* Class A creates anew instance of Class B */ 12    ClassB instClassB = new ClassB( ); 1314    /* Class A invokes a method on Class B */ 15   instClassB.method1B( ); 16 17    /* Class A creates a new instance ofClass C */ 18    ClassC instClassC = new ClassC( ); 19 20    /*Class Ainvokes a method on class C */ 21    instClassC.method2C( ); 22  } 23 24 /* Another method in class A */ 25  public void method2A( ) { 26 27  }28 }

Code Snippet 2: ClassB 1 public class ClassB { 2 3  /*The constructorfor Class B */ 4  public ClassB ( ) { 5 6  } 7 8  /*A method in class B*/ 9  public void method1B( ) { 10 11   /* Class B invokes a method onitself */ 12   method2B( ); 13 14   /* Class B invoked another method onitself */ 15   method3B( ); 16  } 17 18  /*The method 2B */ 19  publicvoid method2B( ) { 20 21  } 22 23  /* The method 3B */ 24  public voidmethod3B( ) { 25 26   /* Class B Creates an instance of classC */ 27  ClassC instClassC = new ClassC( ); 28 29   /*Invoke a method on classC */ 30   instClassC.method1C( ); 31  } 32 }

Code Snippet 3: ClassC 1 public class ClassC { 2 3  /*The constructorfor Class C */ 4  public ClassC ( ) { 5 6  } 7 8  /*A method in class C*/ 9  public void method1C( ) { 10 11  } 12 13  /*The method 2C */ 14 public void method2C( ) { 15 16  } 17 18  /*The method 3C */ 19  publicvoid method3C( ) { 20 21  } 22 }

The above code snippets show the source code for three Java classes.Assuming that the user wants to draw a sequence diagram beginning at thestart point ClassA-method1A, the Call Tree would be derived as follows:

First determine the declaration for method1A in the class ClassA. Methodmethod1A starts at line 9 and ends at line 22 in the code snippet 1. Inthe method method1A determine the methods and constructors that areinvoked. In this case, the following methods and constructors areinvoked.

1. The constructor of ClassB at line 12

2. The method method1B on class ClassB at line 15

3. The constructor of ClassC at line 18

4. The method method2C on class ClassC at line 21

The above represents the first iteration of the tool.

For each of the above, determine the declarations. In so doing, thefollowing is determined.

1. The constructor ClassB starts at line 4 and ends at line 6 in CodeSnippet 2

2. The method method1B of class ClassB starts at line 9 and ends at line16 in Code Snippet 2

3. The constructor ClassC starts at line 4 and ends at line 6 in CodeSnippet 3

4. The method method2C of the class ClassC starts at line 14 and ends atline 16 in Code Snippet 2

For each of the above method and constructor invocations, determine themethods and constructors invoked in them.

1. There are no methods or constructors invoked within the ConstructorClassB

2. Following are the methods and constructors invoked within the methodmethod1B of the ClassB

2.1 The method method2B on class ClassB at line 12

2.2 The method method3B on class ClassB at line 15

3. There are no methods or constructors invoked within the ConstructorClassC

4. There are no methods or constructors invoked within the methodmethod2C of ClassC

The above represents the second iteration of the tool.

For the items 2.1 and 2.2 above determine the declarations. In so doingthe following is determined. The other items are ignored in thisiteration, as they do not have any method or constructor invocations inthem.

2.1 The method method2B of class ClassB starts at line 19 and ends atline 21 in Code Snippet 2.

2.2 The method method3B of the class ClassB starts at line 24 and endsat line 31 in Code Snippet 2.

For each of the above method and constructor invocations (2.1 & 2.2),determine the methods and constructors invoked in them.

2.1 There are no methods or constructors invoked within the methodmethod2B of the class ClassB

2.2 Following are the methods and constructors invoked within the methodmethod3B of the ClassB

2.2.1 The constructor of ClassC at line 27

2.2.2 The method method1C on class ClassC at line 30

The above represents the third iteration of the tool.

For the item 2.2.1 and 2.2.2 above determine the declarations. In sodoing, the following is determined. The other item (2.1) is ignored inthis iteration, as it does not have any method or constructorinvocations in it.

2.2.1 The constructor ClassC starts at line 4 and ends at line 6 in CodeSnippet 3

2.2.2 The method method1C of the class ClassC starts at line 9 ad endsat line 11 in Code Snippet 3.

For each of the above method and constructor invocations (2.2.1 &2.2.2), determine the methods and constructors invoked in them.

2.2.1 There are no methods or constructors invoked within theconstructor ClassC

2.2.2 There are no methods or constructors invoked within the methodmethod1C of the class ClassC

This ends the process, since in both of the above items no furthermethods or constructors are invoked. The Call Tree is derived by puttingtogether the method invocations derived above in the three iterations inthe recursive order in which they are invoked. For the above example,the Call Tree for the specified start point would look like thefollowing.

0. ClassA-Method: method1A (The specified start point)

-   -   1. ClassB-Constructor: Class B (New instance of        ClassB-instClassB1)    -   2. ClassB-Method: method1B (invoked on instClassB1)        -   2.1 ClassB-Method: method2B (invoked on instClassB1)        -   2.2 ClassB-Method: method3B (invoked on instClassB1)            -   2.2.1 ClassC-Constructor: ClassC (new instance                ClassC-instClassC2)            -   2.2.2 ClassC-Method: method1C (invoked on instClassC2)    -   3. ClassC-Constructor: ClassC (New instance of        ClassC-instClassC1)    -   4. ClassC-Method: method2C (invoked on instClassC1)

New instances of classes are created at steps 1, 2.2.1 and 3. Each ofthese may be represented using a different icon in the Sequence Diagram.FIG. 2 shows a Sequence Diagram for the above code snippet examples withthe instances of classes represented across the top of the figure andmessage lines connecting the instances. This information and otherrelated information like line numbers, etc. are stored by the tool in atree data structure.

Thus, as defined herein, a Call Tree is an ordered recursive sequence ofall methods in different classes that are invoked given a method in aclass as the starting point. The Call Tree or a valid sub-tree isrepresentative of the Sequence Diagram. This concept is used in the CodeTree Analyzer tool of the present invention.

Before describing the details of the flow charts, a general descriptionof the use and operation of the Code Tree Analyzer tool will beprovided. The first step in using the Code Tree Analyzer tool isdefining a project workspace. At the minimum, a project workspacecontains the complete paths of the Java source code files that are to beanalyzed to create the design artifacts. In addition to the paths, theproject workspace includes a list called “Ignores”. Ignores is a list ofclass names that will be ignored while creating the different designwork products. Ignores are used to filter out those classes that theuser does not wish to include in the design artifacts generated by thetool.

Design artifacts are the different work products that are created usingthe tool. The tool creates UML-compatible model files for the Sequenceand Class Diagrams and text and rtf files containing the call tree. Thetool also stores data on the work products that have been created. Aspreviously described, this data is later used to determine the impactedwork products when any of the source code files in the project ismodified.

To begin analyzing the Java source files in the project, it is firstnecessary to select a start point. Again, a start point is a combinationof a class name and a method in the class. This is used by the tool tocreate a Call Tree beginning at the selected start point. Additionally,while analyzing the source files, the tool also determines therelationships between the classes. These relationships are used togenerate the Class Diagrams.

The Call Tree that is generated based on the specified start point isused to create a Sequence Diagram that is displayed in the tool. Thedepth of the Call Tree (and hence the Sequence Diagram) can becontrolled by selectively including and excluding Java source code filesin the project. If a call is made into a class for which the source codefile has not been included in the project, the corresponding path in theCall Tree stops there. The tool, however, also displays those classesthat are not in the project but whose methods have been invoked along aCall Tree path. Such classes occur only as leaf nodes in the Call Tree.

The tool includes the feature of providing the ability to update aSequence Diagram by deleting icons, deleting messages or updatingexisting messages. The Sequence Diagram can then be saved inUML-compatible format. The tool remembers all the manual updates to theCall Tree that was used to generate the Sequence Diagram. This data islater used to reapply the manual updates to the Call Tree when thegenerated diagram is impacted due to changes made to any source fileincluded in the project.

The tool also provides features that allow the user to save the CallTree in either text or rtf format. The text format is a detailed versionthat also includes the line numbers in the source files where thevarious methods have been invoked. This may be used to determine thecomplete call tree for a method during debugging. The rtf format is asummary version where calls made by only the method specified in thestart point are included.

The default Class Diagram is generated using the class specified in thestart point as the center of the universe. Only relationships of thisclass with the other classes are displayed. This allows for optionallyincluding other relations using features provided by the tool. Displayedrelations can also be selectively hidden. The UML-compatible model filesare generated based on the currently displayed diagrams.

The tool stores the time stamps for the Java source files in the projectto determine if any source file included in the project has changed.Later, when a project is re-opened, the tool compares the latest timestamps of the source code files with the stored timestamps. A mismatchof time stamps is taken as an updated file.

If the tool finds a source file that has been changed, it is able tosearch through the work products that were previously generated to findout how many of these are impacted and hence need to be updated. Theuser is prompted to update these work products. All manual updates thatwere previously made by the user on the design artifacts can be replayedmanually on the newer versions.

The tool also has a built in differencing algorithm that is capable ofdetermining the extent of change between the original design artifactsand the new ones. The differencing algorithm is applied to the CallTrees used to generate the design artifacts. In many cases the designartifacts can be updated without any manual intervention. The tool iscapable of applying the manual updates made to the original call tree tothe new one.

Additionally, the tool may operate to generate basic code metrics forthe analyzed files. They may include, for example, the physical numberof lines, the number of shipped source instructions, total number oflines containing comments, code to comment ration, etc. This feature mayalso be used, for example, to quickly analyze code and verify it againstcoding guidelines.

The tool first parses the Java source files to determine the VariableDeclarations, Method Declarations, Constructor Declarations, MethodInvocations and Constructor Invocations. The tool then resolves all thevariables to determine their data types. This includes resolving thereturn types for invoked methods to determine the signature of othermethods that use these return values as arguments. The tool alsoresolves method signatures. Then, the method invocation order isresolved for compound statements. This is a preliminary step todeveloping the Sequence Diagram. The tool then generates a Call Treebased upon the selected start point. The Call Tree is then used togenerate a Sequence Diagram. This is simply done by drawing the methodcalls as messages in the Sequence Diagrams in the same order in whichthey appear in the Call Tree.

FIG. 3 shows the basic model for the Code Tree Analyzer tool. The Namesof files 31 and Source files 33 of the Java application program to beparsed are parsed by Java File Parser 35 to identify the blocks definingMethod Declarations, Variable Declarations, Method Invocations andConstructor Invocations. The symbols (the method names, constructornames and variable names) occurring in each of the identified blocks arestored in a Symbol Table. Call Tree Generator 39 takes the Symbol Tableformed by Parser 33 and creates a Call Tree starting at the userspecified method and class. An example Call Tree is shown at 41.

The output from the Call Tree Generator is fed to Model Generator 43.Model Generator 43 generates the Class Diagram and Sequence Diagram. TheIgnores, i.e., the Names of Classes 45 to be filtered out of theseDiagrams are also fed to Model Generator 43 so that the resulting designartifacts generated by the tool is a function of both the specifiedmethod and class starting point and the specified class names to befiltered out. An example of a Filtered Tree is shown at 47. Diagram Data50 represents an intermediate data store that contains graphic data onthe Sequence Diagrams and Class Diagrams. This graphic data is used byViewer & Editor 49 to render these Diagrams. As shown, the SequenceDiagram is displayed by Viewer & Editor 49. The Call Tree, in a treeview, is also displayed in a manner to allow for editing specificvalues. A displayed example is shown at screen 51.

FIGS. 4A-E show flow charts representing the main process flow of theCode Tree Analyzer tool. The Node 11.0 represents the Start Point forthe Main Flow. The Main Flow may be split into the following main steps:

-   -   Creation and maintenance of projects    -   Analysis of the source code files to create the Call Trees and        symbol tables    -   Rendering the Call Trees as a Sequence Diagrams    -   Using the Symbol tables to create Class Diagrams    -   Generating design artifacts    -   Analyzing impacts to previously generated design artifacts and        updating them

The first step in starting the process, is get the Project Name,identified as step 11.1. The Project may be an existing project or a newone to be created by the tool. Each project is identified by a uniquename and consists of an Inputs File, Data File, Time Stamps File,Ignores File and Project Data File.

The Inputs File stores the complete paths of the source code files thatare to be analyzed as part of this project. The Data File stores theunresolved symbol table for the analyzed files. The intent of storingthis data is to optimize the time spent on analyzing the source files ifthe project is re-opened at a later time. During later runs of the toolfor the same project, the tool only analyzes those files that have beenmodified since the previous run of the tool. This helps save time asanalyzing files for a large project with many files takes time.

The Times Stamps File stores the timestamps for the source code files.This data is used in later runs of the tool for the same project todetermine the source code files that have changed. The Ignores Filestores a list of class names that have to be ignored while creating thesequence diagram, class diagram or any other design artifact. This fileallows the user to selectively filter out classes that he is notinterested in displaying in the diagrams. For example, the user maychoose to filter out all the standard Java classes to avoid making thesequence diagrams unmanageable. The Project Data File stores detailsabout the design artifacts created using the tool. This data is used inthe later runs of the tool for the same project to determine theimpacted work products due to changes made to source code files.

In addition to the above, the tool maintains a Master File that containsthe details of all the projects created using the tool. This file storesthe project names and the complete paths of the above files for eachproject. Thus, if a project does not exist in the Master File, a newProject is created, as shown at step 11.3 and in FIG. 5.

At the time of creating a project, the user specifies the source codefiles to be included therein and the symbols to be ignored. The InputsFile and the Ignores File are created as soon as a new project iscreated. However, the timestamps file, data file and project data fileare created at a later time. The master file is only updated with thecomplete paths for these files at the time of project creation.

If the Project already exists in the Master File, the Project file namesare retrieved from Master File 11.4. The tool at this point gets thefull paths of the Inputs File, Data File, Time Stamps File, Ignores Fileand the Project Data File. Next, it is determined whether a Timestampsfile exists for the Project file names.

When a new project is created, none of the associated files for theproject would exist even though the paths for these files would havebeen specified in the Master file at the time of project creation. If aTimestamps file does not exist, one is created, as shown at step 11.7and in FIG. 6. If a Timestamps file does exist, the tool loads theTimestamps for the source code files into the process, as shown at step11.8. These are the Timestamps for the source code files that were savedfrom the previous run of the tool for the same project.

Next, a check is made to determine if a Data file exists, as shown bystep 11.10. If a Data file exists, the Symbol Table for the previous runof the tool for the same project from the Data File is loaded into theprocess. In this run of the tool, only those source code files that havebeen updated would be re-analyzed. The tool compares the current timestamps of the source code files with those saved from the previous runof the tool (in the time stamps file) to determine the updated files.Storing the symbol table from the previous run of the tool for a projectand reloading it at the next run helps save time in reanalyzing all thesource code files.

The node 11.13 in the flow chart represents the Data file. This is abinary file which, in the current implementation for Java, uses standardJava object serialization techniques to save the symbol table datastructures directly. If a Data files does not exist, one is created, asshown by step 11.11.

The Source Code File Names to be analyzed from the Inputs File are thenloaded into the process, as shown by step 11.15 in FIG. 4B. The toolloads the complete paths of the source code files that need to beanalyzed as part of the project from the Inputs File for the Project.The Inputs File is created when a new project is defined.

After loading in the Source Code File Names, each source code file nameis looped through steps 11.17 to 11.26, as shown in FIG. 3B. In doingthis, it is first determined whether a source code file exists for thefirst source code file name. If not, it is removed from the Timestampsand Data File as shown at step 11.18 and the process goes to the nextfile name. If the file does exist for the source code file name, a newtime stamp is obtained for the source code file and a determination ismade at step 11.20 if a loaded timestamp already exists for the file. Ifnot, the Source Code File is read and parsed, as shown by step 11.24 inFIG. 4C. If a loaded timestamp already exists for the file, it isretrieved and compared to the new time stamp, as shown by step 11.22. Ifthe time stamps are different, the Source Code File is read and parsed,as shown by step 11.24 in FIG. 4C. If the time stamps are not different,the file is skipped and the process loops back to the next file.

After reading and parsing the source code files in step 11.24 in FIG.4C, the Parse Tree and Symbol Table data structures for the source CodeFile are updated in step 11.26 and the process loops back to step 11.16in FIG. 4B.

In this regard, it should be understood that the Symbol Table is acollection of data nodes where each node may contain the followingdetails.

-   -   Symbol Name—This is the name of the symbol. Could be set to a        method, variable or constructor name.    -   Symbol Type—This is the type of the symbol. Could be set to any        one of method declaration, constructor declaration, variable        declaration, method invocation or constructor invocation.    -   Method Signature—This is the resolved signature of the method or        constructor. This value is set for all the types but for        variable declaration.    -   Original Method Signature—This is the original unresolved        signature of the method or constructor. This value is set for        all the types but for variable declaration.    -   Data Type—The data type of a variable or the variable on which a        method is invoked.    -   Return Type—The data type of the return value for a method.    -   Block Number—The code block in which the symbol was found.    -   Block Hierarchy—The hierarchy of blocks (nested blocks) where        the last block is the block number in which the symbol was        found.    -   Line Number—The line number in the source code file where the        symbol was found.

The parse tree maintains the block hierarchy for the source code filesanalyzed. It also maintains other attributes of the class in the sourcecode file. For example in the case of Java, this may include the superclasses, the interfaces implemented by the class, the package, etc.

After completing the loops, the next steps are to Save/Update the SymbolTable in the Data File and save/Update the Timestamps File, as shown bysteps 11.28 and 11.30 in FIG. 4C. The Symbol Table is the Resolved instep 11.32 and the Start Point of the Sequence Diagram is retrieved instep 11.33. The details of the Symbol Table Resolve step are shown inFIG. 8.

After retrieving the Start Point, the Call Tree is generated in step11.34, the details of which are shown in FIG. 9. Then a determination ismade of whether an Ignores File exists and if it does not, the processmoves forward to step 11.39 in FIG. 4D wherein a filtered Call Tree as aSequence Diagram is rendered. In this regard, the Ignores File is a textfile that contains a list of class names, one class per line, that needsto be ignored in creating a design artifact.

If an Ignores File does exist, the symbols corresponding to the classesto be ignored are loaded into the process, as shown by step 11.36 inFIG. 4D. After loading the symbols to be ignored into the process, theCall Tree is filtered to remove ignores and the filtered Call Tree as aSequence Diagram is rendered and displayed, as shown by steps 11.39 and11.40.

The Filtered Call Tree is allowed to be manually updated in Step 11.41.The user may delete a node from a tree or edit contents of a node. Themanually updated filtered Call Tree is used to create all of the designartifacts. The tool records the manual updates and saves them as part ofthe Project Data. The tool then takes as input, the design artifact tobe created. This input may include.

-   -   A Sequence Diagram saved in UML-compatible format    -   A Class Diagram saved in UML-compatible format    -   The filtered Call Tree saved in RFT format as a sequence of        steps    -   The unfiltered Call Tree save in Text format as a sequence of        steps

The tool then loads the saved details for the project artifacts from theprevious run of the tool for the Project, if data exists in the ProjectData File. This is shown at step 11.43 in FIG. 4D. Node 11.44 representsthe Project Data File. This may be a binary file that stores thefollowing.

-   -   Complete paths of the design artifact files generated using the        tool.    -   The filtered Call Tree that was used to create each artifact.    -   The manual updates made by the user to the each filtered call        tree.    -   The classes that are referenced in the artifact.

In step 11.45 of FIG. 4D, the tool checks if the artifact specified bythe user exists in the Project Data. If the artifact does not exist inthe project data file, it creates the project artifact. If the projectartifact exists in the Project Data, the tool compares the current datafor the artifact with the previous data loaded from the Project Datafile, as shown in step 11.46 in FIG. 4E. The tool then displays thedifferences, if any between the current version of the artifact and itsprevious version, as shown by step 11.47 in FIG. 4E. The tool alsodisplays the manual updates, if any, made to the filtered call tree inthe previous version of the artifact.

In step 11.49 of FIG. 4E, the tool allows the user to apply the updatesmade in the previous version of the artifact to the new Call Tree. Theuser may make additional updates as well. All the updates re-recorded bythe tool. The tool also recreates the new artifact and saves it, asshown in step 11.50. If this was an existing artifact it overwrites thefile with the new data. The node 11.51 represents the stored DesignArtifacts.

In step 11.52, the tool saves the data for the design artifact in theProject Data File 11.53 also identified as 11.44 in FIG. 4D. Existingdata for the artifact, if any is overwritten. The user may also specifymore design artifacts to be created using the same filtered Call Treedata, as represented by step 11.54. In addition, as shown by step 11.55,the user may specify more start points for the same Symbol Table datagenerated by parsing the source code files in the project to create newCall Trees and design artifacts. To do this, the process loop back tostep 11.33 in FIG. 4C.

FIG. 5 show a process for creating a New Project in the Code TreeAnalyzer tool, as shown in step 11.3 in FIG. 4A. A project in the toolis identified by a unique name. The project name, along with the namesof the files that hold the data for the project (as described in step11.1), are saved in Master File 12.3. The name and location of theMaster File for the tool is predefined. Any number of projects may bedefined in the tool. However, at any one time, only one project may beactive. The user may specify the location where the files for aparticular project are saved.

In steps 12.1 of FIG. 5, the tool prompts the user for the Project Name.In step 12.2, the tool checks the Master File to determine if theproject by that name already exists. If the Project Name exists, thetool prompts the user of such and allows the user to open the existingproject. Only if the Project Name does not exist in the Master File maythe user proceed to create a new project by that name.

In step 12.4 of FIG. 5, the Project Name along with the names (includingthe paths) of the associated files for the project are saved in theMaster File. In step 12.5, the tool takes as input the complete paths ofthe source code files that need to be analyzed as part of this project.The node 12.6 in the flow chart represents the Inputs File, as discussedin regard to Node 11.4 in FIG. 4B. In step 12.7, the tool saves thenames and paths of the source code files in the Inputs File for theproject. The tool then takes as input the names of the classes to beignored while creating the diagrams and design artifacts, as shown bystep 12.8. The node 12.9 in the flow chart represents the Ignores File,as discussed in step 11.37 in FIG. 4D. In step 12.10, the tool saves theclasses to be ignored to the Ignores File for the project. Thiscompletes the creation of a new project. The other files for the projectare created as required during the process of analyzing the source codefiles and creating the design artifacts.

FIG. 6 shows a process for creating a new Timestamps File in the CodeTree Analyzer tool, as shown in step 11.7 in FIG. 4A. The node 13.0represents the start point of the process. The Timestamps File 13.3,corresponding to File 11.9 in FIG. 4A, stores the time stamps for thesource code files from the last run of the tool for the project. Thisdata is used in the next run of the tool for the same project todetermine which source files have been modified. A difference in thecurrent time stamp and the one stored in the Timestamps File for asource code file is assumed to be due to modifications made to thesource code file.

In step 13.1 of FIG. 6, the tool retrieves the name and the path of theTimestamps file for the project from the Master File 13.2 correspondingto Master File 11.4, as shown in FIG. 4A. In step 13.4, the tool thencreates a new Timestamps file as shown at node 13.3 and whichcorresponds to File 11.9 in FIG. 4A. This file is empty to begin with.The tool writes the time stamps for the various source code files tothis file after the source code files have been analyzed.

FIG. 7 shows a process for creating a new Data Files in the Code TreeAnalyzer tool, as referenced by step 11.13 in FIG. 4A. Node 14.0represents the start point of the flow for the creation of a new DataFile. The Data File stores the Symbol Table for the source code filesfrom the last run of the tool for the project. This data is used in thenext run of the tool for the same project to minimize the time spent inanalyzing files that have not been modified between the runs. For suchfiles the Symbol Table from the previous run is used unchanged.

In step 14.1 of FIG. 7, the tool retrieves the name and the path of thedata file for the project from Master File 14.2 corresponding to File11.4 in FIG. 4A. The tool then creates a new Data File 14.3, asrepresented by file 11.13 in FIG. 4A. This file is empty to begin with.The tool writes the symbol table for the source code files to this fileafter the source code files have been analyzed.

FIG. 8 shows a process for resolving the Symbol Table in the Code TreeAnalyzer tool, shown as step 11.32 in FIG. 4C. The node 15.0 representsthe start point of the process. After the source code files are parsedto extract the method declarations, constructor declarations, variabledeclarations, method invocations, constructor invocations and codeblocks, the Symbol Table is resolved. In this process, the data typesfor the variables and the return data types of methods are determined.The objective is to determine the names of the classes, the methodsinvoked on them and the order in which these methods are invoked.Accordingly, the Resolve Symbol Table process replaces those variablenames (either explicit or implicit) in the Symbol Table that representinstances of classes with the corresponding class names. In many cases,the tool may not be able to resolve all the invocations as the sourcecode for the class may not have been included as part of the project.Such unresolved method invocations are represented by a special iconcalled ‘unresolved’ in the sequence diagram. The user may choose todelete this icon before creating the design artifacts.

In FIG. 8, Step 15.1 of the Resolve Symbol Table process first resolvesthe method declarations. The return types of the methods and theirsignatures are determined from the declarations. This is done for themethods and constructors. This is followed by step 15.2 which resolvesthe method invocations. Typically methods are invoked on variables. Thisstep determines the data type of the variables, such that it is possibleto determine the name of the class on which the method is invoked. Thisis done both for the explicitly declared variables and the implicitones. For example, the statement “var1.method1( ).method2( )” has twomethod invocations, one on var1, an explicit variable. The methodmethod2( ) is invoked on the return type of method1( ) and hence is animplicit variable. The tool acts to resolve the classes that correspondto var1 and the implicit variable that represents the return type ofmethod1( ). The tool also keeps track of the constructor invocations inthis step.

Next, the method and constructor signatures are resolved as shown bystep 15.3 of FIG. 8. This involves determining the data types of each ofthe parameters that are passed as arguments to the invoked methods andconstructors. The order in which the methods are invoked is importantfrom the perspective of a sequence diagram. In step 15.4, the toolresolves the order in which the methods are invoked. This step isparticularly important in the case of compound statements that havemultiple method invocations in a single statement. Finally, in step15.5, the symbol table is updated to reflect the resolved methodinvocations.

In FIG. 9, a process is shown for generating the Call Tree in the CodeTree Analyzer Tool, as represented by step 16.0 in FIG. 4C. The CallTree is generated based on the resolved Symbol Table. The Call Tree, inturn, forms the basis for the Sequence Diagram. A start point isrequired to create a call tree. As previously stated, a start point is acombination of a class and a method in the class. Beginning at the startpoint, the tool recursively determines the methods that are invoked.This results in the creation of a tree structure for the Call Tree.

In step 16.1 of FIG. 9, the tool takes as input a combination of a classand a method in the class that represents the start point of the CallTree and hence the Sequence Diagram. The tool retrieves the data for theclass in the start point from the resolved Symbol Table, as shown instep 16.2. Using the data in the resolved Symbol Table, the tooldetermines all the methods and constructors that are invoked within themethod in the start point. These invocations may either be on the sameclass or on other classes. This is shown in step 16.3. As shown in step16.4, the tool loops through each of these invoked methods andconstructors in the method of the start point After the tool completesthe required loops, it retrieves the data for the corresponding classesfrom the symbol table, as shown in step 16.5 of FIG. 9. If the classesare not included as part of the project the methods are not considered,as shown in step 16.6. If the classes are part of the project, themethods that are in turn invoked in each of these methods aredetermined. This is shown by step 16.7. In step 16.8, the process isrepeated until none of the classes on which methods are invoked are partof the project. The resultant tree that is generated out of the aboverecursive steps is the Call Tree for the specified starting point. Thetool keeps track of the variable names of an instance of classes as itis passed across the different methods in the call tree. The tool keepsthis tree in memory and uses it or a filtered version (generated byremoving the classes to be ignored) for generating the Sequence Diagram,which will be described with reference to FIG. 10.

With reference to FIG. 10, there is shown the process for rendering aSequence Diagram. The node 17.0 represents the start point of theprocess that creates the Sequence Diagram from the filtered Call Tree.The sequence diagram is drawn by traversing the filtered Call Tree inorder as shown in step 17.1. For every method invocation in the filteredCall Tree, the process retrieves the invoker and the invoked instances,as shown in step 17.2. Then, for each unique instance of an invokedclass, the tool adds an icon to the Sequence Diagram, as shown in step17.3.

In step 17.4 of FIG. 10, a check is made to see if the invoker and theinvoked instances are the same. If the instances are the same, then acheck is made for a recursive call. If the call is recursive, the tooladds a labeled self-connector. If the call is not recursive, the tooladds a simple self-connector. This is shown at step 17.5. If the invokerand the invoked instances are not identical then add a connector fromthe invoker instance to the invoked instance, as shown at step 17.6.Finally, if a self-invocation has terminated, add a return connector.The above steps are repeated till the entire call tree is traversed. Asshown, the process returns to step 11.40 in FIG. 4D.

With reference to FIG. 11, there is shown a process for rendering aclass diagram from the Code Tree Analyzer tool. The node 18.0 representsthe start point of the process that creates the class diagram from theresolved symbol table for the class. The tool is capable to displayingthe relationships between a selected class and other classes. The userhas to select a class, which is used as the pivot to generate the classdiagram. All relationships in the resulting class diagram are displayedbetween the selected class and other classes that are related to it.Interrelationships between the other classes are not displayed unlessthe user wishes to explicitly include them. FIG. 13 shows a screen shotof a typical Class Diagram.

To begin the process, the tool retrieves the Symbol Table for thespecified class, as shown in step 18.1 of FIG. 11. Then, the tool looksthrough the Symbol Table for the class to get the member variables inthe class, as shown in step 18.3. In step 18.4, the tool looks throughthe Symbol Table for the classes on which methods or constrictors areinvoked. Then, the tool retrieves the super class and the interfacesimplemented by the class, if any, as shown in step 18.5. In step 18.6,the specified class is added as the central icon in the class diagramand in step 18.7, the tool adds icons for the classes that wereidentified in the above steps. FIG. 13 shows a redrawn screen shot of anexample of the central icon and related icons.

The tool defines relationships between the classes based on thefollowing rules.

-   -   If a class has a member variable in the specified class the        relationship is considered to be association.    -   If a method or a constructor is invoked in the specified class        the relationship is considered to be dependency.    -   The relationship between the specified classes and the        interfaces implemented by it is that of realization.    -   The relationship between the specified classes and its super        class is that of generalization.

Also, association takes precedence over dependency. Step 18.8 in FIG. 11uses these rules to draw the relationships between classes. The processends at node 18.9. The data generated in the above steps is used togenerate design artifacts that contain class diagrams.

FIG. 12 shows a redrawn screen shot of an example of a typical SequenceDiagram. The left panel shows the corresponding Call Tree. A Crossindicates a leaf node. A leaf node represents classes that are not inthe project but whose methods have been invoked along a Call Tree path.Similarly, the left panel of FIG. 13 shows the corresponding Call Tree.The purpose of the screen shots, as redrawn in FIGS. 12 and 13, is todemonstrate how the tool may be employed to display the Sequence Diagramand Class Diagram to the user in an interactive mode.

Although description of the process employed by the Code Tree Analyzertool is based upon the start point being a Class, the tool can, withminimal change, also readily be employed to create Sequence Diagramswith Objects as entities of the start point.

It will be understood from the foregoing description that variousmodifications and changes may be made in the preferred embodiment of thepresent invention without departing from its true spirit. It is intendedthat this description is for purposes of illustration only and shouldnot be construed in a limiting sense. The scope of this invention shouldbe limited only by the language of the following claims.

1-15. (canceled)
 16. A system for analyzing static source code of acomputer program, comprising: processor accessible memory arranged tostore source code files to be analyzed; processor accessible memoryarranged to store a selected class name and method in said class fromsaid source code files to be analyzed; a processor unit coupled to saidprocessor accessible memory having said source code files stored thereinand arranged to generate a call tree as an ordered recursive sequence ofall method calls in different classes or instances thereof that areinvoked by said selected method in said selected class and create astored call tree file of said call tree in processor accessible memory;a processor unit arranged to access said stored call tree file andgenerate a sequence diagram from said call tree file; and processoraccessible memory arranged to store said sequence diagram.
 17. Thesystem as set forth in claim 16 including processor accessible memoryarranged to store the time stamps of said source code files asdetermined by a processor unit.
 18. The system as set forth in claim 17,wherein: a processor unit is arranged to update said call tree to formnew design artifacts; processor accessible memory is arranged to storesaid new design artifacts; and said processor unit is arranged tocompare the updated call tree with any previously updated call tree todetermine any differences.
 19. The system as set forth in claim 18wherein said processor unit is arranged to update the call tree for saidnew design artifacts with any of said differences.
 20. The system as setforth in claim 18 wherein a processor unit is arranged to ignoreselected classes when forming design artifacts.
 21. The system as setforth in claim 16 wherein a processor unit is arranged to time stampsource code files as they are processed so that when a sequence diagramis generated any changes made to any source code files that affects thesequence diagram are identified. 22-30. (canceled)
 31. Apparatus,comprising: at least one processor; a memory coupled to said at leastone processor; object oriented source code of a computer applicationprogram to be analyzed stored in said memory, said source code includinga plurality of classes of objects; an analysis program for analyzingsaid source code stored in said memory; input to said at least oneprocessor to cause said processor to select a class name and method inthe class from said classes of said source code and store said selectedclass name and method in the class in said memory; input instructionsfrom said analysis program causing said at least one processor to parsesaid source code to determine variable declarations, methoddeclarations, constructor declarations, method invocations andconstructor invocations; input instructions from said analysis programcausing said at least one processor to resolve all variables todetermine their data type, including resolving the return types forinvoked methods to determine the signature of other methods that usethese return values as arguments; input instructions from said analysisprogram causing said processor to resolve method signatures and themethod invocation order; input instructions from said analysis programcausing said processor to generate a call tree as an ordered recursivesequence of all method calls in different classes or their instancesthat are invoked by said selected method in said selected class storedin said memory; and input instructions from said analysis programcausing said processor to generate a sequence diagram from said calltree by drawing said method calls as messages in the sequence diagram inthe same order in which they appear in said call tree.
 32. The apparatusof claim 31 wherein said sequence diagram is displayed on a displaydevice along with said call tree in a tree view to allow editing.